Hi @noddson. Thanks for being part of GoDaddy Community! Email forwarding plans come free with domain name registrations. There isn't a way to buy more, but you would get more from registering a new domain. While the setup process would require you to specify the new domain as being the source of the credit, you would be able to set them up for any address you control the domain for. Hope that helps.
JesseW - GoDaddy | Community Manager | 24/7 support available at x.co/247support | Remember to choose a solution and give kudos.